A physician is new to the practice and is in the process of being added as a participating provider with insurance companies. Is it illegal to bill services under an already participating provider of the practice if he/she okays it? If not, should the new physician not start rendering services to patients until he/she is a participating provider with ins. comapnies? I'm new to coding and just wanted to know the guidlines for billing under new physicians who are not yet participating providers.